This invention relates to valves that are used in process equipment which operates at elevated temperatures and, more particularly, to valves that have a radiation-absorbing coating on at least a part of the fluid conduit.
Conventional gate valve structures include a valve housing having a fluid conduit and a valve seat, a seal plate that is movable between an open position and a closed position in the fluid conduit, and an actuator mechanism for moving the seal plate between the open and closed positions. The seal plate engages the valve seat and seals the fluid conduit in the closed position. The seal plate may be moved from the closed position to a retracted position and then moved linearly to the open position. The valve may also be operated with the seal plate in a partially open position. The valve housing may include mounting flanges for connecting the valve to other system components.
Gate valves are used in a variety of applications. Different applications may involve liquids, gases and vacuum. Some applications involve the control of gases at elevated temperatures. An example of such an application is in equipment for processing semiconductor wafers, such as etching and chemical vapor deposition (CVD) systems. In some applications of this type, the valve is heated by an external source to minimize process gas deposition in the valve. In prior art systems, the valve is heated with a heater blanket to maintain a set point temperature, such as 80xc2x0 C.
In other applications, a high vacuum pump is mounted on the downstream port of the gate valve. The high vacuum pump may be a cryogenic vacuum pump which may typically operate at 110 Kelvin or lower. When the cryogenic vacuum pump is used to pump a process gas having an elevated temperature, a substantial heat load is placed on the cryogenic refrigerator.
In such applications, it is desirable to limit energy waste so as to limit operating costs. In addition, some countries have mandated energy conservation in such processing systems. Accordingly, there is a need for valve structures and manufacturing methods which achieve energy conservation.
According to a first aspect of the invention, a valve comprises a valve housing having a fluid conduit communicating between an inlet port and an outlet port, a valve closure member that is movable between a closed position which blocks the fluid conduit and an open position retracted from the fluid conduit, and a radiation-absorbing coating on at least a part of the fluid conduit in the valve housing.
In one embodiment, the valve housing includes mounting flanges and the radiation-absorbing coating is disposed on inside surfaces of the mounting flanges. The coating may be black chrome or a black anodized surface, for example. The coating is selected to absorb thermal radiation.
According to another aspect of the invention, a method is provided for making a valve. The method comprises the steps of fabricating a valve having a fluid conduit for carrying a fluid between an inlet port and an outlet port when the valve is open, and forming a radiation-absorbing coating on at least a part of the fluid conduit.